Mesenchymal Stem Cells Downregulate Articular Chondrocyte Differentiation in Noncontact Coculture Systems: Implications in Cartilage Tissue Regeneration

Abstract

While chondrogenesis of mesenchymal stem cells (MSCs) in vitro has been extensively studied, their participation in cartilage tissue repair remains unresolved. This study was designed to elucidate if MSCs affect the phenotype of articular chondrocytes (ACs). A combination of noncontact coculture modes was developed. Human or rabbit MSCs and rabbit ACs (rACs) were encapsulated in alginate hydrogel beads [three-dimensional (3D)] or cultured in a monolayer [two-dimensional (2D)] and subsequently cocultured in the Transwell(®) system. After coculture, cell morphology, growth, deposition of the cartilaginous extracellular matrix (ECM), and gene expression of rACs were investigated. It was found that upon coculture without a cell-cell contact, both 2D and 3D cultured MSCs dramatically induced the morphological transformation of 2D cultured rACs from round to a spindle-like shape, and however inhibited the generation of cellular aggregates of 3D cultured rACs. Most strikingly, a coculture resulted in a significantly less deposition of the cartilaginous ECM, including glycosaminoglycans and collagen type II by both 2D and 3D cultured rACs. Importantly, similar observations were achieved for rACs cultured in an MSC-conditioned medium, confirming the definite paracrine interactions between MSCs and rACs. Based on the analysis of gene expression, this phenotypic change of rACs was not identical as the dedifferentiation. To the best of our knowledge, this is a first study demonstrating that MSCs could downregulate chondrocytic differentiation of ACs and warrants considerations in cartilage tissue repair.

Fibroblast Growth Factor-1 Is a Mesenchymal Stromal Cell-Secreted Factor Stimulating Proliferation of Osteoarthritic Chondrocytes in Co-Culture

“…Combined with our observations that blockade of FGF-1 activity either by inhibitors of FGFRsignaling or by a neutralizing antibody inhibited hPCs proliferation in co-culture pellets and that neutralizing antibodies blocked hPCs proliferation induced by MSC CM, our study identifies FGF-1 as the MSC secreted factor that is responsible for the stimulation of hPCs proliferation in cocultures. Even though our data suggested a positive role of FGF-1 in co-culture pellets, recombinant protein may not be good to replace MSCs in the co-culture system, as secreted factors from MSCs may decrease the deposition of the cartilaginous ECM, including GAGs and collagen type II from articular chondrocytes in a long-term culture [48]. Based on our previous studies, we believe that cell-cell contact between MSCs and chondrocytes in the co-culture system is crucial for maintaining chondrogenic phenotypes.…”

Development of a new co-culture system, the “separable-close co-culture system,” to enhance stem-cell-to-chondrocyte differentiation

“…Aung et al (2011) reported that a co-culture of hBMSCs and chondrocytes without cell-cell contact encouraged the expression level of aggrecan mRNA in hBMSCs. Xu et al (2013) showed that the expression of aggrecan mRNA in chondrocytes was inhibited in an indirect co-culture system. The result of the indirect co-culture system we obtained was consistent with their findings.…”

Enhancing adipose stem cell chondrogenesis: A study on the roles of dexamethasone, transforming growth factor β3 and ascorbate supplements and their combination

“…Total mRNA (up to 2.5 μg) was reverse-transcribed into cDNA using SuperScript® VILO™ Master Mix. cDNA was ampli ied with the TaqMan® Gene Expression Master Mix (Applied Biosystems by Life Technologies, Grand Island, NY, USA) on an ABI 7900HT Sequence Detection System (Applied Biosystems) and probes speci ic for GAPDH, a housekeeping gene that has served as a baseline in several studies on chondrocyteprogenitor interaction and MSC-chondrocyte co-culture [32][33][34][35][36][37], sex-determining region Y (SRY)-box 9 (SOX9), ACAN, Lubricin, Col XI, Col X, VEGF-A, Col I, alkaline phosphatase (ALP), and osterix were used. Known primer sequences for these species appear in Table 1, and where primer sequences are proprietary, the company name and catalogue number are given.…”